On 7.2.2013 5:53, Josh Koffman wrote: > Hi Djula, > > On Tue, Feb 5, 2013 at 6:39 PM, Djula Djarmati wrote: >> What I would do: >> >> 1. 4-cell AA NiMH with good LDO and cheating =3D lower the VCC to 4.5V i= f >> possible. Below 1.2V there is very little energy left in NiMH anyway. > > I considered that, but I don't think I can run the PSoC chips lower > without sacrificing performance of the analog sections. Many 5V chips are specified to work at 4.5V > >> 2. 5-cell AA NiMH with LDO =3D the simplest solution if you can use 5 ce= lls. > > I considered going up to 6 cells, as it's the next easiest number to > get holders for. Not my favourite idea, it'll make the space required > quite a bit more. > >> 3. 2-cell or 4-cell AA NiMH, 2.4V with modern 1MHz boost converter >> without PFM directly, or boost converter with PFM and additional LDO. > > I don't think I understand what you mean by 2.4V here. Wouldn't a 4 > cell system be 4.8V? Also, is the PFM there to give enhanced > efficiency? Why the additional LDO? Not necessarily, 2+2 cells in parallel gets you 2.4V/4000mAh avoiding=20 the need for buck/boost converter. PFM is more efficient but it works by lowering the frequency at low=20 loads, this can also cause more ripple. If you have audio or sensitive analog sections active at that moment,=20 you can get low frequency audible noise. If you don't use analog when=20 the board is in low power state then PFM is fine. Additional LDO is required if the switching noise is excessive. Djula > >> I prefer SANYO Eneloops low self discharge NiMH for any device that will >> be left uncharged a week or two in normal use. I really dislike high >> capacity NiMH that will be half empty every time you need them the most. > > Makes sense. I plan on moving to those eventually. > > Thank you! > > Josh > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .